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WCDMA RNO
RF Optimization
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This lecture introduces the various stages involved
in optimizing a 3G radio network and focuses
mainly on the RF Optimization phase.
Step-by-step approach for the analysis of drive
survey data collected by Scanner and test UE is
presented. The analysis is carried out using the
post processing tool.
Review
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Review
RF optimization will be an ongoing activity and will
need to be revisited as traffic increases in the
network and as new sites are deployed.
In addition, as the network matures, the optimization
process should be enhanced to take into account
statistical data and key performance indicators
collected throughout the network.
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RF Optimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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Network Optimization Phases –
Flow Chart
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Network Optimization Phases – Step 1
Single Site Verification
To verify the functionality of every new site.
Objectives
To ensure there are no faults related to hardware
installation or parameter settings.
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Network Optimization Phases – Step 2
RF Optimization
Once most the sites in a given area are integrated and
verified, RF (or Cluster) optimization could begin.
Objectives
To optimize coverage while in the same time keeping
interference and pilot pollution under control over the
target area. This phase also includes the verification andoptimization of the 3G neighbor lists.
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Network Optimization Phases – Step 3
Services Testing & Parameters Optimization
To be conducted in areas of good RF conditions in order
to exclude any coverage issues. Such testing does not
need to be performed for each cell but the drive route
must include different clutter types and environments.
Objectives
To assess the performance and identify any need forspecific parameter optimization.
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Network Optimization Phases – Step 4
Regular Reference Route Testing & Stats Analysis
Constant monitoring and evaluation of the network
performance can be based on drive test as well as traffic
statistic analysis.
Results of the regular analysis may necessitate re-visits to
the RF optimization and/or parameters’ tuning.
Objectives To identify any new issues that could arise, for example,
as a result of increase in traffic or changes in the
environment.
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RF Optimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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RF Optimization - Preparation
Clusters RF optimization should be carried out for groups or clusters of sites
rather than on single site basis, because the cells’ performance (capacity,
coverage and quality) will influence each other.
Cluster division in a project
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RF Optimization - Preparation
Drive Routes
Cluster drive surveys should include the coverage areas of each cell and
all the major roads and streets as well as any other important locations.
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RF Optimization - Preparation Tools
DTI, Anritsu or Agilent scanner
Huawei U626, Qualcomm UE, etc
Huawei Genex Assistant or Actix Analyzer
GPS
GARMIN Series
GPS
DTI Scanner
(Built-in GPS)
Anritsu
Scanner
Trimble Series
GPS
Qualcomm
TM6250/ 6275
AT Command
Supported
Mobile
Huawei
WCDMA/HSDPAData card
*Support WCDMA
1800/1900/2100M
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RF Optimization - Targets
Item Requirements Comments
CPICH RSCPTarget ≥ - 85 dBm Corresponds to outdoor
measurements.Minimum -95 dBm
CPICH Ec/IoTarget ≥ -8 dB
Applicable for unloaded network.Minimum - 14 dB
Active Set size
(estimated)Target ≤ 3 Based on scanner data.
Pilot pollution
Max % < 10 %% of time a cell is seen as a pilot
polluter.
Threshold 8 dBRelative to best server when cell
is not in Active Set.
UE Tx power Max 95 % For e1a, e1b & e1c
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RF Optimization – Flow ChartDrive Test
Identify any RF Issues
Identify candidate
cells for changes
Identify nature of
required changes
Determine amount
of changes
Implement changes
Repeat Drive Test
Finish
N
Problem Resolved?
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RF Optimization - Solutions
Antenna down tilt
Antenna azimuth
Antenna location
Antenna height
Antenna type
Site location
New site
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RF Optimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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RF Analysis Approaches – Cell Dominance
Cells with no dominance at all
A site was not radiating during the drive survey
Very poor dominance can also be caused by blocking of the
antenna. So a site visit must be made to verify the antenna
clearance.
Cells with either excessive or poor dominance
This could be due to a high site or non-optimum antenna down tilts.
Cells with too large dominance will be causing interference to
adjacent cells resulting in poorer quality and capacity.
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Areas of non-dominance:
Areas where there is not a single clear dominant cell and
where the best server changes too frequently.
Result: Excessive number of soft hand off events reducingthe system efficiency and increasing the probability of call
drops.
UE vs. Scanner Best Serving Cells:
Comparison between the UE and scanner SC plots.
Significant differences between the plots may indicate a
missing neighbor or failed soft handoff problem.
RF Analysis Approaches – Cell Dominance
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RF Analysis Approaches – Cell
Dominance
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RF Analysis Approaches – CPICH
Coverage
Check areas of poor coverage, suggestion value as
below:
Good: RSCP ≥ -85 dBm
Fair: -95 dBm ≤ RSCP < -85 dBm
Poor: RSCP < - 95 dBm
Examine the RSCP coverage on per cell basis in order
to highlight any cells that have too large a footprint.
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RF Analysis Approaches – CPICH
Coverage
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RF Analysis Approaches –
Interference
CPICH Ec/Io Plot
Good: Ec/Io ≥ -8 dB
Fair: -14 dB ≤ Ec/Io < -8 dB
Poor: Ec/Io < - 14 dB
The -8 dB threshold takes into account the expected future interference
increase as a result of increased traffic.
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RF Analysis Approaches –
Interference
Because the RSCP Level is POOR,
the fundamental cause of low Ec/Io is
POOR COVERAGE
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What’s the
problem?
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RF Analysis Approaches –
Interference
RSCP level is GOOD, this will imply
strong SYSTEM INTERFERENCE
BDEFE
BMP
BIG
BDJ
BDK
BDL
BDM
BDE
BDH
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! (%
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! )$ What’s the
problem?
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RF Analysis Approaches –
Interference
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RF Analysis Approaches – UL
Coverage Uplink Coverage (UE Tx Power)
High UE Tx power means possible poor uplink coverage.
Areas of high Tx power should be compared to the CPICH
pilots to verify if the problem only exists on the uplink.
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RF Analysis Approaches – UL
Coverage
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RF Analysis Approaches – Pilot
Pollution
Pilot Pollution Point Define:
Within a certain margin (which is called ThRSCP_Relative) to the
best server
The pilot number (whose strength > best server strength –
ThRSCP_Relative) > ThN (ThN means active set size, normally 3)
Cells which are frequently seen as polluters (e.g. >8% time)
should be marked and investigated.
Pilot Pollution results should be used in conjunction with the
Estimated Active Set Size
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RF Analysis Approaches – Pilot
Pollution
BMI BMH BMMBMK BMJ
BKD
BJG
BKE
BKG
BLE
BLG
BME
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@&.2' @2..:'&2)
ThRSCP_Relative was set 8 dB here
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RF Analysis Approaches – Pilot
PollutionSC Count % in Pollution Set8 206 12.9%
9 165 10.3%
10 157 9.8%
11 156 9.7%
12 148 9.2%
13 135 8.4%
16 95 5.9%
17 94 5.9%
18 76 4.7%
19 74 4.6%
20 73 4.6%
21 56 3.5%
32 54 3.4%
35 39 2.4%
37 33 2.1%
43 19 1.2%
48 8 0.5%
53 7 0.4%
67 3 0.2%
80 2 0.1%
130 2 0.1%
Should be investigated
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RF Analysis Approaches – Pilot
Pollution
Estimated Active Set Size
Another useful measure of pilot pollution is by looking at the
estimated active set based on the scanner data. This plot is
obtained by modeling the network soft handoff parameterswithin Post process tool.
In order to see areas of excessive SHO candidates, the
estimated active set size is allowed to exceed maximum of 3.
This can be done in conjunction with the Pilot pollution
analysis.
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RF Analysis Approaches – Pilot
Pollution Estimated Active Set Size Example
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RF Analysis Approaches – Neighbor List Neighbor List Verification
The neighbor list could be verified and optimized using the
Neighbor List Verification tool within Actix.
Recommendations for Each Cell:
Retain: This indicates that those neighbors have been
confirmed from the drive survey data.
Add: Missing neighbors
Remove: These neighbors that were not measured but are
in the neighbor list.
Careful consideration is needed prior to removing neighbours
since the Actix results are drive route dependent.
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RF Analysis Approaches – Neighbor List
Neighbor List Verification Example
009 576 Retain 018 82 14.2%
Retain 010 46 8.0%Retain 016 31 5.4%
Retain 032 20 3.5%
Retain 011 18 3.1%
Add 130 17 3.0%
Retain 021 17 3.0%
Retain 008 12 2.1%
Retain 020 6 1.0%
Retain 012 5 0.9%
Retain 017 2 0.3%Remove 053 0 0.0%
Remove 019 0 0.0%
Remove 034 0 0.0%
Remove 037 0 0.0%
Remove 013 0 0.0%
Remove 051 0 0.0%
70548 Ajman Central 25.41204 55.447
Nbr SC Sample
Count %Latitude Longitude
Sample
Count ActionSC Cell Site
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RF Analysis Approaches – SHO UE SHO Performance
The success rates for event 1a, 1b & 1c and can be
obtained from Post process tool
um er o ct ve et p ates
Event Count
Event 1a - 328Event 1b - 306
Event 1c - 64
um er o ct ve et p ate omp etes
Event Count
Event 1a - 326
Event 1b - 305
Event 1c - 62
Soft-Handover Success Rate
Event Rate
Event 1a - 99.4
Event 1b - 99.7
Event 1c - 96.9
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RF Analysis Approaches – Drop
Call
Drop Call Analysis - RF related issues :
Poor coverage (RSCP & Ec/Io)
High interference and hence poor Ec/Io
Poor uplink coverage (insufficient UE Tx power)
Poor dominance (best cell changes too frequently
resulting in too many SHO events)
Pilot pollution (too many cells present)
Missing neighbors
Fast change of RF conditions (e.g. turning a corner)
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RF Analysis Approaches – Drop
Call Drop Call Analysis Example 1
Call Drop
RSCP & Ec/Io degrades
BOTH for scanner and UE
Check for Coverage problems
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RF Analysis Approaches – Drop
Call Drop Call Analysis Example 2
Call Drop
Ec/Io (and RSCP) degrades for UE
ONLY while scanner shows no degradation
UE camp on new cell immediately
after drop, and UE did not
measure this cell before Drop
Check the Neighbor
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RF Analysis Approaches – Drop
Call Drop Call Analysis Example 3
Call Drop
Too many and too quick changes
of best server
UE to perform measurements
and SHO in time difficultly
PingPong Handover, need to
improve cell dominance
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RF Optimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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Antenna Adjustment Example RSCP Coverage before Adjustment
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Antenna Adjustment Example RSCP Coverage after Adjustment
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Antenna Adjustment Example RSCP Distribution
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Antenna Adjustment Example Down Tilt from 4 to 6 Result
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Antenna Adjustment Example Down Tilt from 4 to 8 Result
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RF Optimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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Drop Call Analysis Example Drop Call Distribution
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Drop Call Analysis Example
There are total 5 drop calls in the plot.
The example of drop call 1 is analyzed to show the
process of analysis in the following.
Drop call 1 occurred at an area of frequent change of
best server as shown by the scanner scrambling code
plot
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Drop Call Analysis Example CPICH RSCP and Ec/Io before the Call Drop
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Drop Call Analysis Example
Compare Ec/Io from both scanner and UE at the time of the
drop as shown in Figure. This clearly shows the UE Ec/Io to
drop to < -21 dB while the scanner remained above -11 dB.
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Drop Call Analysis Example Best server before and after the Call Drop
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Drop Call Analysis Example
Comparing the best servers from the UE and the
scanner at the time of drop:
Drop Call 1 (UE vs. scanner best server) shows that for
the scanner and UE SC008 is the best server prior to thedrop. However, about 30 seconds before the drop, the
scanner selected SC018 as the best server while the UE
continued to have only SC009 in its active set resulting in
the drop call. Immediately after the drop, the UE camps on
SC018.
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Drop Call Analysis Example UE Active Set and Monitor Set Before and After the Call
Drop
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Drop Call Analysis Example
Conclusion
Examining the UE Active and Monitored set, Figure does not
show SC018 to be measured by the UE prior to the drop.
This scenario resembles a missing neighbor problem
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Drop Call Analysis Example Coverage of Drop Call Point
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Drop Call Analysis Example
Solution:
Looking at drop call Figure clearly shows that at the
location of the drop, SC018 should not be the best server.
Cell SC018 clearly requires some down tilting to control its
interference into the area of Drop 1. To illustrate this,
RSCP coverage of SC018 shows clearly that the cell’s is
extending into a large area. E.g. around the location of
drop call, SC018 RSCP is > -75dBm.
Add the Missing Neighbors
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